speed of light

American  

[speed uhv lahyt] / ˈspid əv ˈlaɪt /

noun

1. Physics, Optics. a fundamental universal constant, the speed at which light and all forms of electromagnetic radiation travel in a vacuum, standardized as 186,282.4 miles per second (299,792,458 meters per second).

   The speed of light, often represented by the letter c, figures prominently in modern physics, as in Einstein’s famous equation E = mc2, which expresses the relation between mass (m) and energy (E).

2. an extremely fast rate.

   They gobbled those appetizers up at the speed of light.

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Etymology

Origin of speed of light

First recorded in 1820–25

Example Sentences

Grant’s work is delicate: He cleaves each strand of a fiber-optic cable for a clean edge, then uses a machine to fuse the hair-thin filaments, which carry digital data at the speed of light.

From The Wall Street Journal

As the flare intensified, X ray output surged dramatically, accelerating particles to speeds of 40 to 50 percent of the speed of light, or roughly 431 to 540 million km/h.

From Science Daily

It led Albert Einstein to propose that the speed of light is constant, a cornerstone idea behind his theory of special relativity.

From Science Daily

"If software and AI models move at the speed of light, energy and hardware move at the speed of physics."

From Barron's

From this disk, intense jets of material were launched at nearly the speed of light.

From Science Daily